The present invention relates generally to fuel tanks for vehicles and, more particularly, to a vapor removal fuel containment fuel tank of a vehicle.
It is known to provide a fuel tank such as a plastic fuel tank in a vehicle to hold fuel to be used by an engine of the vehicle. Manufacturers of plastic fuel tanks are constantly striving to improve impact resistance and barrier properties of their fuel tanks without unduly increasing weight or cost. In plastic fuel tanks, the amount of organic emissions that diffuse through the tank wall is initially very small, but generally increases dramatically after a number of months as the wall materials become saturated with fuel, which can actually increase the wall susceptibility to permeation. However, there is concern that current plastic fuel tanks may have difficulty meeting expected emissions standards.
In a standard plastic fuel tank, there is a continuous diffusion gradient of fuel across the layers of the walls of the fuel tank that actually decrease the effectiveness of the wall as a permeation barrier. If this gradient is interrupted, and the permeates removed before reaching the outer layers of the fuel tank, the emissions can be virtually eliminated.
One commercial approach to resolve this concern is to thicken the wall and/or barrier layers of the fuel tank, which increases the weight, cost and reduces fuel capacity of the fuel tank. Another commercial approach is to protect the fuel tank by metal sheets or shields, which increases the weight and cost of the plastic fuel tank. Yet another commercial approach is to add multiple barrier materials, which add weight and cost.
Therefore, it is desirable to provide a fuel tank for a vehicle that has improved anti-permeation properties without substantially increasing thickness of the tank wall. It is also desirable to provide a vapor removal system for a fuel tank of a vehicle that significantly reduces fuel permeation without unduly increasing weight, complexity, and cost of the fuel tank.
It is, therefore, one object of the present invention to provide a new vapor removal system for a containment fuel tank for a vehicle.
It is another object of the present invention to provide a dual walled plastic fuel tank with an inner fuel containment liner and a vapor purge and recovery system.
To achieve the foregoing objects, the present invention is a vapor removal fuel containment fuel tank for a vehicle including a tank shell having a wall formed from a primary fuel containment layer. The fuel tank also includes a secondary fuel containment layer disposed adjacent the primary fuel containment layer to contain fuel therein. The fuel tank further includes a vapor removal system extending through the primary fuel containment layer to allow fuel vapors that build up between the primary fuel containment layer and secondary fuel containment layer to be removed from the fuel tank.
One advantage of the present invention is that a vapor removal fuel containment fuel tank is provided for a vehicle that has improved integrity during a vehicle impact, improved resistance to fuel permeation, and reduced cost. Another advantage of the present invention is that the vapor removal fuel containment fuel tank has an inner fuel containment liner and an active purge between the layers, virtually eliminating the fuel gradient in the outer wall since the concentrations at the inner surface are kept very low, hence, virtually zero tank emissions from the walls or seams. Yet another advantage of the present invention is that the vapor removal fuel containment fuel tank avoids the use of additional barrier layers that add significant cost and weight and eliminates polymeric tie-layers, removing expensive materials from the fuel tank. Still another advantage of the present invention is that the vapor removal fuel containment fuel tank is relatively easy to adapt for a thermofoming process for manufacturing the fuel tank.
Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings.